Question

................... regulate the opening and closing of the stomata and also perform photosynthesis.

• A. Pallisade parenchyma
• B. Guard cells
• C. Companion cells
• D. Spongy parenchyma

Answer 1

Answer: (B)

Guard cells

Guard cells are bean or dumble shaped specialized cells in the epidermis of leaves, stems and other organs that are used to control gas exchange. The guard cells are produced in pairs with a gap between them that forms a stomatal pore. Opening and closure of the stomatal pore is mediated by changes in the turgor pressure of the two guard cells. Photosynthesis depends on the diffusion of carbon dioxide ($C{O}_2$) from the air through the stomata into the mesophyll tissues. Oxygen ($O_2$), produced as a byproduct of photosynthesis, exits the plant via the stomata. Thus, the correct answer is option B.